A known form of closure is the so-called "snap-on" closure which comprises a circular cap portion with a downwardly extending skirt. Upon the internal periphery of the skirt is an annular closure bead or series of beads that interlocks with a corresponding bead or groove on the neck of the container. The interlock provides an interference that resists removal of the cap from the container, and provides a seal between the container opening and the closure by firmly holding the closure upon the neck. The cap forms a tight seal upon the neck of the bottle, but is usually easily removed by an upward pressure on the cap periphery. The cap is easily reapplied again to the container by merely snapping it onto the neck with a downward pressure. The snap-on closure is often favored over so-called screw-on cap closures, because, unlike with a screw-on closure, the user of a snap-on closure needs only to provide the force to overcome resistance of the interlock and does not need to apply a force or torque to achieve the seal between the container neck opening and the closure. Therefore, a snap-on closure can provide a more reliable seal, especially when the closure is used by persons of varying strength and dexterity. Furthermore, the snap-on closure is less subject to misalignment which would prevent the seal, as might occur with a cross thread on a screw-on closure.
A problem with the simple snap-on closure is that it can be removed and reclosed without any indication that the container has been opened. It is, therefore, possible for someone to tamper with the contents of the container with no indication thereof to a subsequent user. Furthermore, although this closure is convenient and easy to use, some snap-on closures allow for a young child to open and gain access to the contents of the container. However, opening resistance may be increased and surface projections may be removed from snap-on closures to make it difficult for a child to open the container. In the packaging of certain substances, such as poisonous liquids, cleaning solutions, medicines, and the like, it is desirable to have such a closure resistant to opening by a child. It would be desirable, therefore, to have a closure which has the superior sealing characteristics, the ease of reopening for adults, and the ease of reclosure of the snap-on closure, and which also provides evidence of being opened after the first opening. It would also be desirable that such a closure be resistant to the efforts of the child to remove the closure on the first opening and subsequent reopenings.
A suggested solution to the problem of no tamper indication is disclosed in U.S. Pat. No. 4,037,746 to Ver Hage. Therein is disclosed a snap-on type closure with an extension of the downwardly extending skirt. On the inner surface of the skirt extension is a second annular retention bead that also fits into a corresponding groove on the neck of the container. The interlock of the retention bead and groove are such that the closure cannot be removed by an ordinary person without the retention bead being removed.
In order that the retention bead be detached from the closure so that the upper portion of the closure can be removed, a scored portion is provided between the two annular beads of the closure and a tab is provided on the lower extended portion of the skirt. The closure is opened by grasping the tab and tearing off the lower portion of the skirt along with the retention bead. The closure can then be removed and reclosed like a snap-on closure.
Another solution has been suggested by Wortley et al. in U.S. Pat. No. 4,362,253. This closure is similar to the Ver Hage closure in that it comprises a snap-on closure with a retention bead. Between the retention bead and the bead of the snap-on portion of the closure is a thin web or series of spaced webs. In this closure the retention bead is detached from the upper closure snap-on element by providing a lug on the upper portion. The user applies an upward pressure on the lug, which tears the web and allows the upper snap-on portion of the closure to be separated from the lower portion with the retention bead. The upper snap-on portion can then be reclosed and reopened like the snap-on closure.
While the Ver Hage and Wortley et al. closures provide a tamper-indicating closure, this benefit is accompanied by problems. One problem is that large graspable tabs or lugs are required for the first opening of the container in order to remove the lock bead. Since the closure is usually of a smooth plastic material, these tabs or lugs are often difficult to grasp, which causes difficulty in applying sufficient force to remove the lock bead portion. Thus, the opening of the container is often attended by frustration and painful fingers as the user tries to grasp the tab or push the lug to separate the retention bead portion.
This problem can be partially moderated by increasing the size of the tabs and/or lugs. However, as the size of the the tabs and/or lugs increases, there may be interference with the function of the closure as well as with access to the contents of the container.
Integral tabs or lugs also complicate the initial application of the closure to the container, which is usually done by automatic custom-designed applicators during the packaging operation. The production time, material requirements, and costs for producing the closure are also increased by the use of tabs and/or lugs. The increased material requirements lead not only to higher costs, but also to extra cooling time in the molding of the closure. Integral tabs and lugs also require the use of multi-piece molds, which increases costs and further complicates the molding operation.
Another problem with closures having integral tabs and lugs, is that they are generally not child-proof. In fact, lugs on the closure cap may actually assist the child in opening the container.
M. R. Fields, et al. disclose in U.S. Pat. No. 3,455,478 a general type of closure with a detachable retention ring similar to the above closures. The retention ring has an inner annular retention bead that prevents removal of the closure while the retention ring is attached to the closure. This closure does not have tabs or lugs to remove the retention ring, but uses screw/thread mechanism to separate the retention ring from an upper screw-on type cap when the closure is opened for the first time. As the closure cap is unscrewed, the frictional drag of the retention ring on a groove on the container neck, and the upward force caused by the screw mechanism, tear a frangible zone between the retention ring and the screw-on cap portion. The retention ring is thus removed from the closure. The screw-on cap portion of the closure is then unscrewed to open the container. A problem with this closure is that it is often difficult to apply sufficient torque to break the frangible zone. Weakening the frangible zone to ease removal partially solves this problem, but this also makes it easier for a child to also remove the cap, thus defeating any child-proof qualities of the closure. Also, after the first opening of the closure and the breaking of the frangible zone, there is no child-proof feature provided. Furthermore, this closure is of the screw-on type, and does not have the desirable sealing, reclosure, and reopening characteristics of a snap-on closure.
A common feature of the previously described prior art closures, is that the means for applying the force to open the closure for the first time to remove the retention bead, such as tabs, lugs, or the use of a thread/screw, are incorporated into the closure element itself. This results in a compromise of the qualities of the closure, for example, with the Ver Hage and Wortley et al. closures, there is increased material requirements and, thus, increased costs. In the Fields et al. closure, the sealing and reopening/reclosing qualities of the snap-on closure are sacrificed by use of a screw-on type closure. Furthermore, as discussed above, none of these closures are completely satisfactory in providing an easy removal of the lock ring when the closure is opened for the first time, and none of these closures are child-proof to a satisfactory extent, neither upon the initial opening nor upon subsequent reopenings.
In view of these prior art closure problems, an object of the invention is to provide a snap-on type closure that has a tamper-indicating feature, but without additional material of construction. The first opening of the closure should require a minimum of strength, and yet be difficult for children to accomplish. Furthermore, after the closure is first opened, the closure should be reclosable and reopenable in the simple manner of the snap-on closure but provide resistance to the reopening by a child.
Other objects of the invention will become evident in the description that follows.